Adult-onset neuronal intranuclear inclusion disease initially presenting with prominent gastrointestinal symptoms: a case report

Abstract Background Neuronal intranuclear inclusion disease (NIID) is a rare and progressive neurodegenerative disorder, distinguished by extreme clinical heterogeneity that frequently results in diagnostic delays. While gastrointestinal symptoms are common in NIID, the prolonged gastrointestinal-dominant prodrome—lasting years before neurological signs emerge—remains under-recognized in adult-onset cases. Case presentation We report a 59-year-old female evaluated in the gastroenterology department for a four-year history of recurrent vomiting and abdominal pain. Comprehensive investigations, including endoscopy, abdominal CT scans, and laboratory studies, excluded significant structural or inflammatory pathology. She was admitted on March 30, 2024, for another episode of abdominal pain and vomiting. Over the disease course, her symptoms extended beyond the gastrointestinal tract to include cognitive decline, urinary retention, and two episodes of impaired consciousness. On April 2, 2024, she acutely developed stroke-like manifestations—somnolence, loss of speech, and left-sided hemiparesis—requiring urgent transfer to neurology. Brain MRI demonstrated cerebral atrophy, extensive confluent white matter hyperintensities with frontoparietal predominance, and characteristic linear DWI hyperintensities along the corticomedullary junction. Genetic testing ultimately confirmed neuronal intranuclear inclusion disease (NIID). Conclusion This case underscores the fact that NIID may present with prominent gastrointestinal symptoms in its early stages. Therefore, NIID should be considered in the differential diagnosis for patients with chronic unexplained gastrointestinal complaints, particularly those with concurrent autonomic or subtle neurological dysfunction. A timely diagnosis requires comprehensive neurological assessments, characteristic MRI findings, and definitive genetic testing.